Scale WebGL cavas to browser window size

I'm trying to scale Unity WebGL content based on the contents of the window. I could manage this on Unity 5.5.4, with the following HTML. The problem is, if I try this same method on Unity 2017.2, using the following... It correctly scales when it initially loads, but if the window is resized while it is running, it will no longer automatically update the resolution, whereas it did on the previous version. Is this something that's possible, or it is a limitation of the way WebGL is handled by Unity? A solution that would dynamically resize, or even just scale the content would be appreciated.